Intermitting clump and thump from left rear strut, mount maybe?

The dealer cannot duplicate this thumping coming from the left rear side of my 2005 impala, I tell them it's the strut mount but they want it to get a little worst before they replace it, anyone one else have this annoyiny clunk and thump?

The dealer cannot duplicate this thumping coming from the left rear side of my 2005 impala, I tell them it's the strut mount but they want it to get a little worst before they replace it, anyone one else have this annoyiny clunk and thump? check your spare tire in the trunk and tighten up the wing nut that keeps the jack in place,that will work

The dealer cannot duplicate this thumping coming from the left rear side of my 2005 impala, I tell them it's the strut mount but they want it to get a little worst before they replace it, anyone one else have this annoyiny clunk and thump? Yes it was the jack in the trunk,the wing nut was very loose and the hole where the jack rests is open metal with no carpet,so everytime i would hit even the smallest or bigger bumps in the road it would move up and down producing a metal banging sound through out the whole back end of the car which was very good at sounding like a bad strut or a bad strut mount, i found this problem myself but the dealer did not even think about checking the spare tire and jack,takes to much effort for the know it all mech at gm dealership